Remoistening adhesive



. Patented Novg12,

P -ATENT OFFICE.

, REMOI$TENWG ADHESIVE Hans F. Bauer, Chicago, Jordan V. Bauer, ElmwoodPark, and Don M BawlenGeneva, Ill assigners to Stein, Hall ManufacturingCompany, a

Chicago, 111-, a corporation of Delaware.

1 No Application January 20, 1939, Serial No. 251,916

, .13' Claims. ,"(cL 134-234) This invention relates to improvements inadhesive manufacture and more particularly to'a new and improved type ofamylaceous remoisten- 5 -'I' he presentapplication .is a bontinuation inpart of our copending applications, Serial Nos.

- 224,110 filed August 10, 1938; 226,074 filed August 22, 1938;235,480.filed October '17, 1938;-an 247,138 filed December 22, 1938. Theterm amylaceous adhesive is employed "herein to refer to those types ofadhesives which are prepared from'starche's and starchdegradationproducts, such as. dextrines or starch gums.

' The-expression. remoistening adhesive is-eml6 ployed to describe-anadhesive which is applied to a material as a coating and dried, andwhich,

on being moistened, will develop tackiness and act as asuitable'adhesive for bonding the material to other materials." v Atpresent, large amounts of gummedpaper, suitable for such purposes aslabels, stamps and envelope seals, are prepared with dextrineadhejsives; but dextrine adhesives have never been successful inreplacing animal glue adhesives in the field of gummed tape for sealingthe heavier types of boxes. or for gum'medpaper or fabric which is to beused for purposes wherein it is required that the adhesive coating onbeing moistened will develop rapidly strong adhesiveproperties and set39 up very rapidly to form a bond. In our applications previouslyreferred to, ,we have describednew and improved typesjof adhesives madefrom base materials of certain specified characteristics, intimatelydispersed "or associated with certain auxiliary materials. Wethave alsodescribed new and improved types of g'ummed tapes'made from suchadhesives. r

These adhesives afford many improvements I and advantages-overthe-animal glue type of ad- 40 hesive and possess remoisteningadhesiveproperties which are superior to most of the animal glue adhesives nowin usef They can be emvployedin thoseuses where heretofore only gummedtape made from animal glue orflsh glue remoistening adhesives could besatisfactorily used. In carrying out the inventionsdescrlbed in theaforesaid patent applications; we have stressed particularly the use ofurea or of a water soluble urea, in conjunction with the starchler typesof amylaceous conversion products the urea-acting as a plasticizingagent and' at the same time counteractingthe retrogradation ofincompletely degraded portions of the amylac'eQ lS M56 material to aless soluble form.

- of the filtrate pipetted into a platinum dish. After the addition of 2drops of 1% phenolphthalein solution, N/l hydrochloric acid is addedcau- One of the objects of this inventionis to provide new and improvedtypes of remoistening adhesives, characterized by exceptional adhesivestrength and suitable for the strongest type of remoisteningapplications; Other objects will 5 appear hereinafter. L

In accordance with this invention, it has been found-that water solublenitrates which have a' r solubilizing or dispersing actionon starchdegradatio'n products, may be employed inamylal0 ceous: adhesivecompositions made from the ,starchier types of amylaceous conversionproducts and are adapted to act as plasticizing agents and to counteractthe retrogra'dationof incompletely degraded portions of the'amylaceousmaterial to 1 -a less soluble form.

We hav'efound, in accordance with this invention, thatby employing watersoluble nitrates in themanner' hereinafter more specifically disclosedwe are able to prepare superior remoisten- 20 ing adhesives whichdevelop extreme tackiness immediately upon being remoistened do not tendto slip or slide on the surface to which they are applied even underconditions of considerable tension or sidewise pressure and havesufl'icient 5 7 cohesiveness while still wet to hold surfaces togetherwhich would normally tend to spring ap'art. Our base materials, for thepurpose of this invention, comprise the starchier types of amylaceousconversion products which have been con- 30 vertedto the followingcharacteristics:

' -(a) A dextrine content of less than 55%, as determined by the methodof Babington, Tingle and Watson, Journal of the Society of ChemicalIndustry 37 (191 a) 257'. method is as fol- 3 lows: A

The sample (1 grmJ is warmed in a cc. graduated, flask with 30 cc. ofwater until just 'gelatinized and cooled quickly; 50 cc. of a coldsaturated barium hydroxide solution is next 40 added (the flask beingmeanwhile shaken), followed by enough'water to bring the total volume to100 cc. The solution is filtered through a dry 15 cm. paper andanaliquot portion (5 0 'fcc.)

tiouslytill the neutral point is just'passed. A

' faint pink color is then restored by the addition 0 of two or threedrops of thebariumhydroxide solution. A weighed quantity (about 10grms.) of sand is added and the dish is heated on a, water bath. I hesand should be stirred when'almost dry to expose the maximum surface tothe air, 55

lated oven and dried to constant weight at 120 6., below whichtemperature crystallized barium chloride is dehydrated. Dextrin gumbeing byl groscopic; precautions must be taken accordingly. The dish isnow heated strongly, but not beyond the temperature necessary for thecomplete combustion of the organic matter. During ignition the sandshould be well stirred at 0 intervals to allow full exposure to the air.The dish and contents are then cooled and weighed. The diiierence inweight before and after ignition represents the dextrine gum in 50 cc.of filtrate, i. e., in half the weight of sample taken.

(b) The viscosity of degraded or dextrinized starches is a definiteindication of the extent to which the starch has been dextrinized orderaded. A suitable conversion product for the purpose of this inventioncomprises a dextrinized or.degraded starch which when cooked in theproportions of 1 part of conversion product to 1 /2 parts of water to190 F. and then cooled to 125 F'. gives a viscosity reading within therange of seconds to 400 seconds, preferably within the range of 25seconds to 150 seconds on a Stormer viscosity apparatus, the readings inquestion being the time for 100 revolutions of the viscosimeter cylinderusing a 100 gram weight. -The Stormer viscosimeter used gave a readingor 5.6 seconds with water at 125 F. and-a read- 4 ing of 2.4 secondsrunning free with the viscosimeter cup empty, these readings being thetime required for 100 revolutions of the viscosimeter cylinder using a100 gram weight. 85 (0) Within the limits given under (a) and (b) wepreferably employ the following types of con- 7 version products: 7

(1) British gums having a solubility greater than about 60%, preferably70% to 95%, in water at 75 F., and

(2) Incompletely dextrinized starches oi the white dextrine type havinga solubility in water from about 3% to about The' term British gum" isemployed to refer a to those types of starch degradation products thatare formed by roasting or heating starch without, or at the most, withvery small amolmts of acid catalysts as diflerentiated from dextrineswhich are formed from starch by roasting or '50 heating the starch withrelatively large amounts of aeid patalysts... For tlre.purposepf thisinvention it is preferable to employ as the base material a British gumtype of amylaceous conversion product, but it will be understood thatany amylaceous material having the general characteristics given under(a) and (b) may be employed in conjunction with the auxiliary materialsmentioned hereinafter under (d) for thep p of making a remoisteningadhesive according to this invention.'

(d) The base material given under (a) and (b) is mixed with or dispersedwith a water soluble nitrate, preferably with the influence of 5 heat,the nitrate being employed in effective amounts to plasticize thecomposition and to counteract the retrogradation of the moreincompletely degraded portions of the amylaceous base material to a lesssoluble form. Among the water soluble nitrates which may be employed'are ammonium nitrate, sodium nitrate, potassium nitrate and guanidinenitrate. As previously indicated, the nitrates apparently act asplasticizing agents, tending to inhibit the 75 formation of checks orcracks, and they may be r 2,220,987 after which the dish is transferredto a well regu used either alone or in conjunction with other materialshaving-a similar solvent and plasticizing action, as for example, watersoluble ureas, including urea and thiourea and/or-water solublethiocyanates, .including potassium thiocyanate and sodium thiocyanate,with or without additional plasticizing agents, as for example,glycerinejethylene glycol, diethylene glycol and other polyhydricalcohols, or with sodium lactate and other substances having aplasticizing 'efiect. In general, it is preferable to employ from about3% to about 30% of a water soluble nitrate, with or without about 1% toabout 10% of a plasticizer, such as glygerine, polyhydric alcohols orother plasticizers.

(e) In addition to the foregoing auxiliary materials a relatively smallamount of a viscosity increasing agent for amylaeeous dispersions may\be employed to improve the result obtained. A

preferred agent for this purpose is borax. So-

dium aluminate and similar soluble aluminates function somewhatsimilarly to borax in increasing the viscosity of amylaceousdispersions. The viscosity increasing agent may also be formed in situin the adhesive composition, for ex-' ample, by incorporating boric'acidin the adhesive and adding an alkali in the remoistening conversionproducts used as base materials which tends to,destroy the retackproperties.

It may be observed that the water soluble nitrates apparently have amodifying action on borax, which inhibits the insoiubilizing action 01'the borax on the amylaceous conversion products. Hence, according tothis invention, remoistening adhesives may, be prepared from basematerials. having the general characteristics given under (a) and (b),together with borax and a plasticizingagent such as a water solublenitrate, which is normally solid, with or without a plasticizing agentsuch as glycerine. which is nprmallydiquid. A By theuse oi' thespecifically defined combina- .tion of materials herein disclosed,remoistening adhesives may be produced which are at least equivalent inadhesive properties to the better grades ot animal glue remoisteningadhesives. Additionally, it'ha's been found that by the in"- troductionof borax or other viscosity increasing agent into the water used toremoisten the adhesive film, it is possible to obtain adhesive resultsfar superior to animal glue remoistening adhesives.

The followingexamples will illustrate several of the preferredadhesiveformulae of this invention and a comparison of their adhesiveproperties with other types of remoistening adhesives, as indicated by aMcLaurin gummed tape tester, which is an instrument made by the Thwingq-Albert Instrument Company, Philadelphia, Pennsylvania, U. S. A. It willbe understood that the results of these tests may vary somewhatdepending upon humidity and temperature conditions, but the comparativeresults" definitely showed the superiority of adhesives made inaccordance with this invention.

Where borax is employed. in the.

water or some other compound adapted to react mixture was then cooled to80 F. and applied Example! I Parts Tapioca conversion product 9'7 Boraxi3- Sodium nitrate 20' Water 90' Glycerine 5 'The above materials weremixedtogether and cooked to a temperature of about 180 F. The

to paper and dried. 'Thetapioca conversion- .product used was one havinga dextrine content of 9% as determined by the method of Babington,Tingle and Watson, supra, a solubility of,

about 12.6% and a fluidity of 38 seconds as de-.

termined on a Stormer-viscosimeter in the'inan -v ner previouslydescribed.

After being allowed to airdry for four days, the McLaurin test onthistape when moistened withwater averaged about 78. A higher test wasobtained when the tape was moistened with a saturated solution of borax.

' mixture was then cooled to 80 F. and applied to paper and dried. The.British gum used was one having a solubility of 85% in water at 75 F.and a dextrine content of 36% as determined by the method of Babington,Tingleand Watson, supra.

McLaurin tests on tape prepared with this adhesive composition averagedabout 83 when the tape was moistened with water. was obtained when thetape was moistened with a saturated solution of borax.

It should-be understood that the examples of adhesive formulae givenabove are for the purpose of illustrating the novel character of theinvention and for the purpose of making clear the principles and therelative value of the means by which the result is. obtained. It is notdesired to limit theinvention by the specific examples, inasmuch asnumerous variations may be made in the character of the adhesive baseand in the proportion of other ingredients used withsavajpotato, andsweet potato, orfrom grain starches, for example, corn, rice and wheat.In generaLconversion products made from the root starches are preferredand give the best results regardless of whether the conversion productis an incompletely dextrinized product or a; British gum. Less desirableresults are obtained with starches derived from grains, particularlywhere the conversion product is a dextrine or anincomthose specialefiects for which theuse of such materials is known to the adhesive art.Small amounts of sulfonated oils, as, for example, Tur- A higher testkey red oil, inproportions of, say, 0.5% to about 3% may be included inthe adhesive compositions of-this invention.

In, such instances where it is desirable, the disclosed adhesivecompositions may be mixed with compatible adhesive materials made fromanimal glue, fish glue, casein, starch, natural gums and water solublenatural or synthetic resins.

Adhesive compositions made in accordance with the present invention,when applied asa coating and dried and thereafter remoistened,d'evelopextreme tackiness immediately and are characterized by a veryhigh rapidity of set. As contrasted with animal glue adhesives; theyhave practically no odor; One of the further the preferred adhesives aresubstantially neutral and contain no ingredients which are harmful topaper or fabric, or to the user in case the adhesive is moistened withthe tongue. tion, adhesive films prepared as we have described, areextremely flexible-and do not readily check, crack or chip off. from thematerial to which they are applied.

Adhesive compositions of this type maybe used not only as moisteningadhesiveon gummed tape or other sheet materials, but also in otherremoisteningadhesive applications; for example, on high speed machinesfor making containers, receptacles, andother articles.

Having thus described the invention, what we claim as new and desire tosecure by Letters Patent of the United States is: i

I 1. A remoistening-adhesive composition formed from a British gumhaving a dextrine content less than 55%, as determined in the mannerhere- In addiin described, a fluidity within the range of about -10%glycerine, the amount of glycerine being greater than the amount ofborax.

' 2. A remoistening'adhesive composition comprising an amylaceousconversion product having a dextrine content of less than 55%, asdetermined in' the manner herein described, and a fluiditywithintherange of about 15 seconds to about 400 seconds, as determinedin the manner herein described, intimately associated with a viscosityincreasing agent in effective amounts to increase the retack propertiesof said adhesive and a plurality of plasticizing agents efiective to,inhibit checks and cracks of dried films of said adhesive, one of saidplasticizing agents being normally solid and comprising a water solublenitrate in proportions from about 3% to about 30% by weight of theconversion product, and another being normally liquidand comprising apolyhydric alcohol in proportions from about 1% to about 10% of saidconversion product.

3. A remoistening adhesive composition formed from a British gum havinga dextrine content less than about as determined in the man ner hereindescribed, and a fluidity within the range of about 15 seconds to about400 seconds, as determined in the manner hereindescribed,

" intimately dispersed with a soluble borate in amounts effective toincrease the viscosity but not greater than about 5% by weight of saidBritish gum and about 3% toabout 30% of a water solublenitrateplasticizer for said adhesive, having a 4' modifying, action onsaid borate, said adhesive possessing .strong adhesive properties andbeing capable of forming dried flexible coatings. which,

when moistened, develop tackiness and set to a 5- strong bond rapidly;-

.15 about 30% 01' a water soluble nitrate, said adhesive possessingstrong adhesive properties and being capable of forming dried flexiblecoatings, which, when moistened, develop tackiness and set toastrongbond rapidly. 5. A remoistening adhesive composition comprisinganamylaceous conversion product having a dextrine content .less thanabout 55%, as determined in the manner herein described, and a fluiditywithin the range of about 15 seconds to about 400 seconds, as determinedin the manner herein described, intimately dispersedand associated witha water soluble nitrate in amounts from about 3% to about by weight ofthe amylaceous conversion product, said adhesive 30 possessing strongadhesive properties and being capable of forming dried, flexiblecoatings, which when moistened developtackiness and set rap- -idly.

6. A remoistening adhesive formed from a British gum having'a dextrinecontent less than about 55%, as determined in the manner hereindescribed, a fluidity within the range oi about 15 seconds to about 400seconds, as determined in the manner herein described, and a solubility01 at least 60% in water at 75 F., intimately dispersed with a solubleborate normally having an 'insolubilizing action on said British gum ineffective amounts to increase the viscosity of said adhesive, and anormally solid plasticizer for said adhesive comprising a water solublenitrate and having a solubilizing action on said British gum and amodifying action on said bursts in amounts efl ective in inhibiting theinsolubilizing action 01' said borate on said-British gum andininhibiting l0. retrogradation 01!. said British gum'to a less solubleform, said adhesive; strong adh-' sive properties andbeing capable offorming dried flexible coatings, which, when moistened, developtackiness and set to a strong bond rapidly.

56 -7. A remoisteningesive formed from an incompletely dextrinized rootstarch conversion product converted to a solubility of about 8% to aboutin water at 75'? F., a viscosity within the range of about 15 seconds toabout 400. sec-,

o0 onds, as determined in the manner herein described, and a dextrinecontent less than about as determinedin the manner herein described,intimately dispersed with a soluble borate normally having aninsolubilizing action on said conversion product ineffective amounts toincrease the viscosity of said adhesive, and a normally solidplasticizer for said adhesive comprising a water soluble nitrate havinga solubilizing action on said conversion product and a modi- 70 iyingaction on said borate in substantial amounts efiective in inhibiting theinsolubilizing action of said borate on the said conversion product andin inhibiting retrogradation of said conversion product to a lesssoluble form, said adhesive-pos- 7 s'essing strongadhesiveproperties'and being capable of forming dried flexible coatings, which,when moistened, develop tackiness and set to a strong bond rapidly,

8. A remoistening adhesive composition comprising an amylaceousconversion product having 5 a dextrine content less thamabout 55% asdetermined in the manner herein described, and a fluidity within therange of about 15 seconds to about 400 seconds, as determined inthe'manner herein described, intimately dispersed with a plastici'zing 0agent in substantial amounts effective to inhibit the retrogradation orincompletely degraded portions 01 the amylaceous base material to a lesssoluble form, said plasticizing agent comprising a water solublenitrate.

9.-.A remoistening adhesive composition oomprising an amylaceous basematerial consisting substantially of a. British gum having a solubilityin water of at least at 75 F. and a dextrine content less than about55%, as determined in the manner herein described, together with afluidity within the range of about 15 seconds to about 400 seconds, asdetermined in the manner herein described, intimately associated with aplasticizing agent in amounts effective to counteract the re- 25trogradation'oi incompletely degraded portions of the amylaceous basematerial to a less soluble form, andvcomprising a substantial amount oi.a water soluble nitrate.

10. Aremoistening adhesive composition com- 30 prising an amylaceousbase material composed substantially of an incompletely dextrinizedstarch having a dextrine content less than about 55%. as determined inthe manner herein dcscribed, a fluidity within the range of about 15seconds to about 400 seconds, as determined in the manner hereindescribed, and a solubility within the range of about 3% to about 50% inwater at 75 'F., intimately dispersed with a plastlcizing agentcomprising a water soluble nitrate in amounts eflective to counteracttheretrogradation oi incompletely degraded portions of the amylaceousbasematerial to a less soluble orm. 1

11, A remoistening adhesive compositioncomprisingan amylaceousconversion product having adextrine content less than about 55%, as de-:termined in the manner herein described, and a fluidity within the rangeof about 15 seconds to about 400 seconds, as determined in the mannerherein .described,'intimately dispersed with asoluble borate and'atIeast'pne plasticizingag'ent, comprising a substantial amount of a watersoluble nitrate, adaptedto counteract the retrogradation of incompletelydegraded portions of the amylaceous base material to a less solubleform, said adhesive possessing strong adhesive propertlesand beingcapable of forming dried flexible H coatings which, when moistened,develop tackiness and set to a strong bond rapidly.

- 12. A remoistening adhesive composition comprising an amylaceousconversion product having a dextrine content less than-about 55%, as'determined in the manner herein described; and a 05 fluidity within therange of about 15 seconds .to

about 400 seconds, as determined'in the manner herein described,intimately dispersed with a vis cosity' increasing agent for amylaceousdispersions in amounts less than about 5% by weight of the amylaceousconversion product and at least one plasticlzing agent comprising asubstantial amount of a. water soluble nitrate adapted to counteract theretrogradation o1 incompletely degraded portions of the amylaceous basematerial 76 cosity increasing agent in efi'ective amounts to increasethe retack properties of said adhesive and at least one plasticizingagent comprising a water soluble nitrate in efiective amounts to inhibitchecks and cracks in dried films of said adhesive, said adhesivepossessing strong adhesive properties and being capable of forming driedflexible coatings, which, when moistened, develop tacki' ness and set toa strong bond rapidly.

HANS F. BAUER. JORDAN V. BAUER. DON M. HAWLEY.

